Photographic processing method utilizing frozen aqueous solutions



Oct. 3, 1967 E. H. LAND 3,345,172 PHOTOGRAPHIC PROCESSING METHOD UTILIZING FROZEN AQUEOUS SOLUTIONS Filed Dec. 1, 1964 illustrating the method of the United States Patent Filed Dec. 1, 1964, Ser. No. 415,086 8 Claims. (Cl. 96-48) This invention relates to photographic methods and, more particularly, to methods of treating exposed photosensitive image-recording sheet material with liquids having substantially the viscosity of water to produce visi ble images in the sheet material.

The method of the invention finds particular utility in a photographic process in which a visible positive image is formed in a sheet from an exposed silver halide emulsion by diifusion-transfer reversal effected by an aqueous alkaline liquid, having the viscosity of Water and including a silver halide developing agent, impregnated into the sheet. In processes of this type, it is important not only that the quantity of the liquid impregnated into the sheet be accurately controlled and the liquid be uniformly distributed, but liquid agents of this type are subject to and must be protected against deterioration, e.g., evaporation, aerial oxidation, pH changes, etc., when exposed to the atmosphere.

Objects of the invention are: to provide in a photographic process of the type described, a novel and improved method of applying a predetermined quantity of a liquid processing agent having the viscosity of water to a surface of a photosensitive image-recording sheet for impregnation into the sheet; and to provide a method as described in which the liquid is uniformly distributed in the sheet material over a predetermined area thereof and is confined, handled and applied in such a manner as to preclude spillage of the liquid and protect the liquid against deterioration due to exposure to the atmosphere.

Other objects of the invention are: to provide a substantially dry method of applying a non-viscous photographic developing liquid to one side of an image-recording sheet for impregnation into said sheet; and to provide a method as described in which the processing liquid is protected against deterioration due to exposure to the atmosphere by freezing the liquid into a solid body, and said liquid is applied to the sheet by pressing and moving the solid body of frozen liquid against one side of the sheet.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process in volving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing wherein:

FIGS. 1 and 2 are somewhat schematic sectional views of apparatus for performing the method of the invention illustrating said method, and

FIG. 3 is a similar view of another form of apparatus invention.

Ofiice The present invention is particularly concerned with a method of treating a succession of exposed sections of a combination photosensitive image-recording and imagereceiving sheet material with a non-viscous liquid, that is, a liquid having substantially the viscosity of Water, to form visible positive prints in the exposed and processed sections of the sheet material. Typical sheet materials and processes useful in the method of the invention are disclosed in the copending US. patent applications of Edwin H. Land, Ser. Nos. 368,621 and 368,622 filed May 19, 1964, both now abandoned. The sheet material employed in the process comprises, for example, a support, such as paper, having thereon a layer of a light-sensitive silver halide emulsion and an outer layer comprising a translucent material such as finely divided titanium dioxide, calcium carbonate, magnesium oxide, etc., dispersed in a suitable permeable colloidal carrier or matrix such as gelatin which is permeable to the processing liquid. This outer layer may also contain silver precipitating nuclei and is sufficiently transparent to permit photo-exposure of the light-sensitive layer therebetween while, at the same time, being sufiiciently opaque to provide the requisite background for a positive silver image transferred thereto and to mask the negative image formed thereunder.

The process performed with this photosensitive sheet material is particularly useful for duplicating documents so that the apparatus employed for processing according to the method of the invention is, in the preferred form, designed to contain processing liquid sufficient to process a succession of exposed sheets or sections of a sheet and apply the liquid to each exposed section. An example of the composition of a processing liquid suitable for this purpose and useful in the method of the invention is as follows:

Water 4-amino-2,S-dimethylphenol gm This aqueous and highly alkaline liquid-processing agent is preferably applied to the same side of the sheet material as the translucent layer for impregnation into the light-sensitive image-recording material, i.e., silver halide, to form a visible silver image by diffusion transfer of image-forming substances from the image-recording material.

The process may be considered to be substantially dry When and because the liquid is confined or contained in such a way as to preclude spillage or contact with components of the apparatus outside of the container prior to application to the sheet and is applied to one side of the sheet, rather than to both sides of the sheet as is the case when the sheet material is immersed in a container of the liquid, and the wet portion of the sheet is prevented from contacting components of the sheet. In other words, in the dry method of liquid application described and constituting the invention, the liquid contacts only the container, the applicator and the sheet material, and quantities of the liquid are stored prior to application so as to prevent spillage and protect the liquid from deterioration. Dry methods of applying non-viscous liquids pose the additional problems of applying a predetermined quantity of the liquid uniformly over the section of the sheet material to be treated.

react extremely slowly, if at all, with the atmosphere so a that little or no precautions are required to prevent contact between the liquid and the atmosphere.

To apply a predetermined quantity of the liquid uniformly to one side of a sheet, a quantity of the liquid at least suflicient to process a section of sheet material is frozen to form a solid body, preferably elongated and having a dimension approximately equal to one dimension of the section or area (e.g., rectangular) of image-recording sheet to be treated. The elongated body is pressed against the surface of the sheet so as to make contact therewith over an area extending from edge to: edge of the section to be treated and is moved transverse-- 1y of its long dimension across the section to'be treated. The pressure of the body of frozen liquid against the sheet causes melting of the liquid in the region of contact between the frozen body and sheet and the liquid as it melts is immediately absorbed by the sheet so that there is noseparation or deterioration of the constituents of the liquid. Melting and application of the liquid in the region of contact can be further promoted by sliding the frozen body relative to and in contact with the sheet and, in the preferred form of the invention, a combination of rolling and sliding contact is achieved. The quantity of' liquid applied to the sheet in this manner is dependent up on such factors as the pressure applied to hold the body against the sheet, the temperature of the liquid, the rate of movement of the frozen body and sheet relative to one another and, in the embodiment in which substantially all of the frozen liquid is utilized, the quantity of liquid initially present and composing the frozen body. These factors are obviously subject to reasonably accurate control so that the amount of liquid (which is very small) absorbed into the exposed image-recording sheet material can be predetermined with substantial accuracy. Moreover, in accordance with the invention, the liquid is in a solid condition during the major portion, if not all, of the time it is outside of a container and in contact with the sheet material so that it is protected against deterioration due to exposure to the atmosphere and spillage, and contamination of other components of the apparatus are prevented.

In the embodiment of the method of the invention illustrated in FIGS. 1 and 2, a quantity of the liquid sufficient to treat a plurality of sections of exposed image recording sheet material is rapidly frozen to form an elongated body having a length preferably equal to one dimension,

e.g., width, of the section of sheet material to be treated. Body 10 is stored in a container 12 having walls 14'with channels 16 through which a refrigerant is circulated to maintain body 10 in a solid condition; and a cover comprising two sections 18 movable from the closed position shown in FIGURE 1, to the open position shown in FIG. 2. Container 12 provides a recess or chamber 20 for containing frozen liquid body 10 and includes a backing member 22 engaged between the walls of the container and mounted on-a reciprocating shaft 24 for movement within chamber 20 toward and away from the open end of the chamber. Backing member 22 and shaft 24 are also formed with channels 16 through which a refrigerant is circulated, and backing member 22 is formed with peripheral grooves for allowing the atmosphere within chamber 20 to pass from side to side of the backing member during reciprocal movement of the backing member.

Body 10 of the frozen liquid is frozen with a retaining member 28 adapted to be releasably coupled with backing member 22 embedded in the body for coupling the body with the backing member.

Container 12 is mounted with the open side thereof uppermost, beneath a roll 3d rotatable'about an axis extending in the direction of elongation of body 10, and functions to support a sheet 32 against body 10 and move the sheet relative to the body in contact therewith. The apparatus also includes a support plate 34 for guiding sheet 32 in a generally horizontal plane, container 12 and roll 39, means for rotating the roll, means for moving cover sections 18 to an open position as a sheet 32 is moved into the space between the roll and container, and means for moving rod 24 upwardly to lift frozen body 10 upwardly into contact with the lower surface of the sheet which is supported against the frozen body by roll 30. The pressure between the frozen body and sheet may be controlled easily and may be retained constant by providing a compression spring between shaft 24 and the means for moving the shaft, or between roll 30 and whatever the fixed means on which roll 36 is mounted.

In the method illustrated by FIGS. 1 and 2, a sheet 32 or section thereof to be treated, is advanced along support plate 34 into the space between roll 30 and the container and as the leading edge of the section to be treated enters the space, cover sections 18 are opened and the frozen body is raised by backing member 22 into contact with the lower surface of the sheet at the leading edge of the section to be treated; Roll 30 is rotated to move the sheet across and in contact with the frozen body of liquid and as the trailing edge of the section to be treated reaches the frozen body, the latter is lowered into chamber 20 and cover sections 18 are closed. Chamber 20 is maintained at a temperature just low enough to maintain body 10 of frozen liquid in a solid condition and prevent any melting thereof, and a small portion of the body is raised from the container only long enough for the liquid to be applied to a sheet so that melting of the frozen body occurs only at the portion thereof in contact with the sheet. Chamber 20 is preferably slightly larger than frozen body 10 in order to allow for freedom of movement of the body while maintaining the walls of the chamber as close as possible image-recording sheet, and this time may range from minutes to months so long as the liquid is retained in a solid frozen condition such that no melting occurs. It is possible to store the solid, frozen developing liquid without deterioration in an ordinary atmosphere containing such gases as oxygen and carbon dioxide, which would ordinarily react with the constituents of the developing liquid to cause deterioration thereof.

In another embodiment of the method of the invention illustrated. by FIG. 3, freezing of the developing liquid is effected immediately prior toapplication to the image-recording sheet primarily for the purpose of facilitating application of a predetermined uniformly distributed quantity of the liquid in a manner which could be termed dry. In this embodiment, the liquid is rapidly frozen as a thin layer on the surface of a cylindrical heat-absorbing roll or drum and, immediately following freezing,that is, within a few seconds at most, the layer of frozen liquid on the drum is pressed into and moved in contact with the image-recording sheet to melt the 7 way of example in FIG. 3, and comprises a cylindrical applicator roll or drum 36 constructed to provide for the circulation of a refrigerant within the drum in order to maintain the drum at a temperature such that the developing liquid will freeze almost instantaneously as it is applied as a sheet to the drum. Drum 36 is rotated and the liquid is applied to an upper portion of the rotating drum by means providing a narrow elongated passage 38 through which the liquid emerges as a sheet equal in length to the width of the section of sheet material to be processed. Passage 38 is formed in a nozzle 40 including a chamber 42 containing the processing liquid, a passage 44 between chamber 42' and a passage 44 for conducting the liquid from chamber 42 to passage 38, a valve 46 within passage 44 for controlling the flow of liquid through the passage, and a thermal insulating member 48 between the section of nozzle 40 including chamber 42, passage 44 and valve 46 and the section thereof including passage 38. This latter section is formed with passages 50 through which a refrigerant can be circulated for cooling the developing liquid prior to emergence from passage 38 and deposit and freezing upon drum 36.

The width of passage 38 and the adjustment of valve 46 are such that the developing liquid emerges from the passage as a thin sheet which is immediately frozen upon contacting the drum to form a solid body or sheet 52 on the surface of the drum composed of a predetermined quantity of liquid such that substantially all of the liquid is applied to the sheet. The means for applying the liquid to an image-recording sheet, designated 54, include a guide member 56 and a backing roll 58 mounted in juxtaposition with drum 36 beneath the drum with the axes of the drum and roll in the same plane and spring biased upwardly toward drum 36. Roll 58 is preferably rotated so that its surface moves at a faster linear rate than the surface of drum 36 so that a sheet advanced between the drum and roll by rotation of the roll is held by the roll in both rolling and sliding contact with layer 52 of the frozen developing liquid. This arrangement is preferred because it promotes friction between the sheet and frozen layer tending to cause melting of the frozen layer and more complete utilization by absorption by the sheet of the frozen developing liquid coated on the drum.

The rate of flow of the liquid, rotation of drum 36 and advancement of sheet 54 by roll 58 are all interrelated to achieve complete utilization of the liquid frozen on the drum. However, some residue of frozen liquid may remain on the drum and it is desirable that it be removed prior to the application of fresh liquid to the drum and for this purpose there is provided a scraper blade 60 biased against the surface of drum 36 by a spring 62 and a trough 64 located beneath the edge of scraper blade 60 Where the latter contacts the drum, for collecting frozen developing liquid removed from the drum by the scraper blade. The surface of drum 36 preferably comprises or is coated with a material which is not only unaffected by aqueous alkaline developing liquids, but which is so constituted that the developing liquid will adhere to it at least sufficiently to be rubbed in contact with the image-recording sheet, whereas the material comprising the surface layer of roll 58 has a high coefficient of friction in order to engage and advance the image-recording sheet relative to the surface of the drum. It is further contemplated that in this embodiment of the invention, heating means may be provided for raising the temperature of the liquid-impregnated sheet to advance the silver halide diffusion-transfer reversal process and/or dry the sheet. Such heating means may comprise a heater within roll 58 or means located beneath the sheet for heating the sheet by radiation and/or conduction. It may also be desirable to preheat the sheet, for example, by providing heating elements in support member 56 and, in this manner, promote the thawing of the frozen processing liquid. While the heat absorbing members have been shown as including passages for the circulation of a coolant liquid, it is contemplated that other types of refrigeration systems are equally useful including, for example, thermoelectric devices.

The method of the invention provides the answers to the three most basic and important problems associated with the processing of light-sensitive sheet materials with non-viscous developing liquids, namely, preventing deterioration of the liquid during prolonged storage and/ or application to the sheet material, applying a uniformly distributed predetermined quantity of the liquid to only one side of a sheet, and doing so by a process which is dry in the sense that the liquid is confined to a container, applicator and one side of the sheet. Spillage is prevented and the highly akaline liquid, including the liquid impregnated into one side of the sheet, is prevented from contacting other components of the apparatus. The liquid is stored, handled and applied by apparatus which is relatively simple, and application of the liquid is performed rapidly, accurately and reliably. Freezing of the developing liquid substantially eliminates the danger of deterioration and spillage, and application of the frozen liquid by pressing and moving a solid body of the frozen liquid against one side of the sheet insures application of an accurately predetermined quantity of liquid of unstable, but known, chemical composition evenly and uniformly distributed to only one side of a light-sensitive image-recording sheet.

Since certain changes may be made in the above process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is: 1. The method of treating an exposed photosensitive image-recording sheet with an aqueous liquid having substantially the viscosity of "water to produce a visible image in said sheet, said method comprising:

rapidly freezing a quantity of said aqueous liquid containing reagents capable of reacting with differentially exposed photosensitive image-recording mate rial to produce a visible image, said liquid being frozen in the form of a substantially solid body having at least one dimension approximately equal to one dimension of the section of said sheet to be treated; and while maintaining said body of frozen liquid in a substantially solid condition, supporting said body in contact with one side of said sheet over an elongated area located adjacent an edge of said section and extended to opposite edges of said section; and

simultaneously pressing said body against said sheet and moving said sheet and body relative to one another transversely of said elongated area to cause melting of said body in the region of contact with said sheet and impregnation of said sheet with said liquid resulting from said melting.

2. The method of claim 1 wherein said body is moved relative to said sheet in sliding contact therewith.

3. The method of claim 1 wherein said body is moved relative to said sheet in rolling contact therewith.

4. The method of claim 1 wherein said body is moved relative to said sheet in combined sliding and rolling contact therewith.

5. The method of claim 1 wherein said quantity of liquid is approximately equal to the amount required to treat said section of said sheet and is rapidly frozen by application to the surface of a heat absorbing member immediately prior to application to said sheet; and substantially all of said quantity of said liquid frozen on said member is applied to said section of said sheet.

6. The method of claim 5 wherein said surface of said heatabsorbing member is cylindrical and said member is mounted for rotation about the axis of said surface; said of frozen liquid to make sliding and rolling contact with 10 said sheet and prolonging the period during which said sheet is in contact with said frozen liquid.

8. The method of claim 1 wherein said sheet is heated 7 immediately following impregnation with said liquid.

a 8 References Cited UNITED STATES PATENTS 630,500 8/1899 Graeme 9589 3,079,272 2/1963 Greig 96-48 3,236,650 2/ 1-966- Lirnberger 96-50 FOREIGN PATENTS 357,195 2/1929 Belgium.

NORMAN G. TORCHIN, Primary Examiner.

C. E. DAVIS, Assistant Examiner. 

1. THE METHOD OF TREATING AN EXPOSED PHOTOSENSITIVE IMAGE-RECORDING SHEET WITH AN AQUEOUS LIQUID HAVING SUBSTANTIALLY THE VISCOSITY OF WATER TO PRODUCE A VISIBLE IMAGE IN SAID SHEET, SAID METHOD COMPRISING: RAPIDLY FREEZING A QUANTITY OF SAID AQUEOUS LIQUID CONTAINING REAGENTS CAPABLE OF REACTING WITH DIFFERENTIALLY EXPOSED PHOTOSENSITIVE IMAGE-RECORDING MATERIAL TO PRODUCE A VISIBLE IMAGE, SAID LIQUID BEING FROZEN IN THE FORM OF A SUBSTANTIALLY SOLID BODY HAVING AT LEAST ONE DIMENSION APPROXIMATELY EQUAL TO ONE DIMENSION OF THE SECTION OF SAID SHEET TO BE TREATED; AND WHILE MAINTAINING SAID BODY OF FROZEN LIQUID IN A SUBSTANTIALLY SOLID CONDITION, SUPPORTING SAID BODY IN CONTACT WITH ONE SIDE OF SAID SHEET OVER AN ELONGATED AREA LOCATED ADJACENT AN EDGE OF SAID SECTION AND EXTENDED TO OPPOSITE EDGES OF SAID SECTION; AND SIMULTANEOUSLY PRESSING SAID BODY AGAINST SAID SHEET AND MOVING SAID SHEETD AND BODY RELATIVE TO ONE ANOTHER TRANSVERSELY OF SAID ELONGATED AREA TO CAUSE MELTING OF SAID BODY IN THE REGION OF CONTACT WITH SAID SHEET AND IMPREGNATION OF SAID SHEET WITH SAID LIQUID RESULTING FROM SAID MELTING. 